Carbon metabolism in spores of the arbuscular mycorrhizal fungus Glomus intraradices as revealed by nuclear magnetic resonance spectroscopy

• Published in: Plant physiology (Bethesda) Vol. 121; no. 1; pp. 263 - 271
• Main Authors: Bago, B, Pfeffer, P.E, Douds, D.D. Jr, Brouillette, J, Becard, G, Shachar-Hill, Y
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Physiologists 01.09.1999; American Society of Plant Biologists
• Subjects: Agronomy. Soil science and plant productions; amino acid metabolism; Amino acids; Amino Acids - biosynthesis; arginine; Betaine - metabolism; Biological and medical sciences; carbohydrate metabolism; Carbon; Carbon - metabolism; Carbon dioxide; Carbon Dioxide - metabolism; colonization; Darkness; degradation; Economic plant physiology; Fatty acids; fructose; Fundamental and applied biological sciences. Psychology; Fungal spores; Fungi; Fungi - growth & development; Fungi - metabolism; Glomus intraradices; glucose; Hexoses; Hexoses - metabolism; hyphae; life cycle (organisms); Lipid Metabolism; Lipids; Living conditions; Magnetic Resonance Spectroscopy; mannitol; Mannitol - metabolism; Mycorrhizal fungi; NMR; Nuclear magnetic resonance; nuclear magnetic resonance spectroscopy; Parasitism and symbiosis; Plant physiology and development; Plant-Microbe and Plant-Insect Interactions; spectral analysis; Spectroscopy; Spore germination; Spores, Fungal - growth & development; Spores, Fungal - metabolism; sugars; Symbiosis; Symbiosis (nodules, symbiotic nitrogen fixation, mycorrhiza...); Terrestrial environments; Time Factors; trehalose; Trehalose - metabolism; uptake; Urea; Symbiosis; Symbionte; Hexose; Germination; Biological transport; Phycomycetes; Lipids; Storage carbohydrate; NMR spectrometry; Metabolism; Spores; Fungi; Endomycorrhiza; Mycorrhiza; Thallophyta
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.121.1.263

Arbuscular mycorrhizal (AM) fungi are obligate symbionts that colonize the roots of over 80% of plants in all terrestrial environments. Understanding why AM fungi do not complete their life cycle under free-living conditions has significant implications for the management of one of the world's most important symbioses. We used (13)C-labeled substrates and nuclear magnetic resonance spectroscopy to study carbon fluxes during spore germination and the metabolic pathways by which these fluxes occur in the AM fungus Glomus intraradices. Our results indicate that during asymbiotic growth: (a) sugars are made from stored lipids; (b) trehalose (but not lipid) is synthesized as well as degraded; (c) glucose and fructose, but not mannitol, can be taken up and utilized; (d) dark fixation of CO2 is substantial; and (e) arginine and other amino acids are synthesized. The labeling patterns are consistent with significant carbon fluxes through gluconeogenesis, the glyoxylate cycle, the tricarboxylic acid cycle, glycolysis, non-photosynthetic one-carbon metabolism, the pentose phosphate pathway, and most or all of the urea cycle. We also report the presence of an unidentified betaine-like compound. Carbon metabolism during asymbiotic growth has features in between those presented by intraradical and extraradical hyphae in the symbiotic state.